Optical spectroscopy and ultrafast pump-probe study on Bi${}_2$Rh${}_3$Se${}_2$: evidence for charge-density-wave order formation

Abstract

The parkerite-type ternary chalcogenide Bi${}_2$Rh${}_3$Se${}_2$ was discovered to be a charge density wave (CDW) superconductor. However, there was a debate on whether the observed phase transition at 240 K could be attributed to the formation of CDW order. To address the issue, we performed optical spectroscopy and ultrafast pump-probe measurements on single crystal samples of Bi${}_2$Rh${}_3$Se${}_2$. Our optical conductivity measurement reveals clearly the formation of an energy gap with associated spectral change only at low energies, yielding strong evidence for a CDW phase transition at 240 K. Time resolved pump-probe measurement provides further support for the CDW phase transition. The amplitude and relaxation time of quasiparticles extracted from the photoinduced reflectivity show strong enhancement near transition temperature, yielding further evidence for the CDW energy gap formation. Additionally, a collective mode is identified from the oscillations in the pump-probe time delay at low temperature. This mode, whose frequency decreases gradually at elevated temperature, could be naturally attributed to the amplitude mode of CDW state.

6 pages, 6 figures, to be published in Phys. Rev. B

References in corpus (6)

• Use of X-ray scattering functions in Kramers-Kronig analysis of reflectance
• Single-particle and collective mode couplings associated with 1- and 2-directional electronic ordering in metallic RTe${}_3$ (R = Ho, Dy, Tb)
• Revealing extremely low energy amplitude modes in the charge-density-wave compound LaAgSb${}_2$
• Superconductivity versus structural phase transition in the closely related Bi${}_2$Rh${}_{3.5}$S${}_2$ and Bi${}_2$Rh${}_3$S${}_2$
• Optical study of phase transitions in single-crystalline RuP
• Gap-dependent quasiparticle dynamics and coherent acoustic phonons in parent iron pnictide CaFe2As2 across the spin density wave phase transition

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• Origin of the density wave instability in trilayer nickelate La${}_4$Ni${}_3$O${}_{10}$ revealed by optical and ultrafast spectroscopy
• Optical spectroscopy and ultrafast pump-probe study of a quasi-one-dimensional charge density wave in CuTe
• Optical spectroscopy and ultrafast pump-probe study of structural phase transition in 1T'-TaTe2
• Collapse of density wave and emergence of superconductivity in pressurized-La${}_4$Ni${}_3$O${}_{10}$ evidenced by ultrafast spectroscopy
• Highly anisotropic transient optical response of charge density wave order in ZrTe${}_3$